Method of continuously casting metal using carbon dioxide for cooling



L. M. HERFF May 19, 1970.v

METHOD -OF CONTINUOUSLY CASTING METAL USING CARBON DIOXIDE FOR COOLING FiledDc. 21, 1967 LOU/S M. HERFF Alforney United States Patent Olce 3,512,573 Patented May 19, 1970 3 512,573 METHOD OF CON'IINUOUSLY CASTING METAL USING CARBON DIOXIDE FOR COOLING Louis M. Herff, Ross Township, Allegheny, Pa., assignor to United States Steel Corporation, a corporation of Delaware Filed Dec. 21, 1967, Ser. No. 692,558 Int. Cl. B22d 1.7/12

U.S. Cl. 164-82 1 Claim ABSTRACT OF THE DISCLOSURE Molten metal is teemed into a cooled, how-through, tubular mold. A coolant gas (c g., CO2) is discharged into the gap at the bottom of the mold, between the walls thereof and the casting, caused by shrinkage of the Casting away from the walls, thus increasing the absorption of heat from the casting.

This invention relates to continuous casting and, in particular to a method and apparatus for increasing the removal of heat from the casing while still in the mold and just prior to its exit therefrom.

Continuous casting is ordinarily carried on by teeming liquid metal into a tubular, flow-through mold, provided with forced cooling such as a jacket for circulating water. The problem is to abstract suflicient heat from the casting into the mold Walls so that a skin of adequate thickness to contain the liquid center is formed by the time any point along the casting reaches the lower end of the mold. The problem is the more serious because the slight shrinkage of the casting resulting from solidiication impairs the good thermal conductivity initially existing between the metal and the mold walls.

I have invented a method and apparatus whereby the aforementioned difficulty is largely obviated. According to my method, I inject a gas such as carbon dioxide into the spaces between the casing and mold walls which open up on shrinkage of the casting. My apparatus includes nozzles positioned appropriately adjacent the bottom of the mold walls. The nozzles are mounted on manifolds connected to a suitable gas source.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:

FIG. l is a side elevation of the apparatus of my invention in operative relation to a continuous-casting mold, and

FIG. 2 is a cross-section taken along the plane of line II-II of FIG. 1.

Referring now in detail to the drawings, a mold of the tubular, dow-through type is mounted on a suitable support (not shown) and s provided with a cooling-water jacket 11. Molten metal is teemed into the mold from a ladle 12 suspended thereabove and the cooling efrected by the loss of heat from the metal to the mold walls causes the formation of a skin 13 confining the molten center portion of a columnar slab 14 which descends from the mold progressively as it is formed, between guide rolls 15 and 16. The thickness of the skin increases gradually and the resulting shrinkage of the casting opens up slight gaps 17 between the mold walls and the casting.

The foregoing is typical of continuous casting as practiced heretofore. In accordance with my invention, I discharged jets 18 of gas such as CO2 under substantial pressure, into gaps 17. To this end, nozzles 19 are spaced along manifolds 20 adjacent the bottom of the mold and the manifolds are connected to a gas reservoir by a pipe line 21 including a pressure regulator 22. Jets 18 elect a strong cooling of the slab skin in several ways. In the first place, contact or convection cooling occurs. In the second, the CO2 decomposes, absorbing more heat. Some oxidation of the casing surfaces is effected by the oxygen released by CO2 decomposition. The oxide layer thus formed on the casting radiates heat more effectively than the original metal surface. As a result of all these factors, the ow of heat across gaps 17 is many times what it would be in the absence of the injected gas and the absolute temperature of the casting surface is substantially reduced. l

The CO2 also serves to lubricate passage of the casting through the mold and reduces wear on the interior surfaces of the mold walls. The slightly oxidized condition of the contacting surfaces, furthermore, reduces the possibility of welds forming therebetween.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention as set forth in the claim.

I claim:

1. In a method of continuously casting metal, the steps comprising teeming molten metal into the upper end-of a cooled, tubular, flow-through mold, withdrawing a columnar casting from the lower end of the mold and injecting carbon dioxide upwardly into said lower end between the mold walls and the surface of the emerging casting.

References Cited UNITED STATES PATENTS 2,791,812 5/ 1957 Dangelzer et al 164-283 3,099,053 7/ 1963 Eliot 164-64 3,293,707 12/1966 Olsson 164-83 3,344,840 10/1967 Buehl et al 164-66 X 3,353,584 1l/l967 Atkin 164-73 X 3,353,585 ll/l967 Wentzell 164-64 X FOREIGN PATENTS 526,061 6/ 1956 Canada.

I. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, Assistant Examiner U.S. Cl. X.R. 164-66 

